Telephone apparatus



April 16 1929- H. SELL ET AL TELEPHONE APPARATUS Filed Aug. 2'?, 1925 v, Vf,

Patented Apr. 16, 1929.

UNITED STATES PATENT OFFICE.

HELMUT SELL AND BERNHARD LANGENBECK, 0F BERLIN-SIEMENSSTADT, GERMANY,

ASSIGNORS T0 SIEMENS & HALSKE, AKTIENGESELLSCHAFT, 0F SIEMEJSI'SSTADT,A NEAR-BERLIN, GERMANY, A CORPORATION OF GERMANY.

TELEPHONE APPARATUS.

Application filed August 27, 1925, Serial No.

The present invention relates to telephones, especially telephones of small size and the main object of t-he invention is to improve apparatus of the said kind to eiiect a. true sound reproduction anda very high efhcleney in spite of a compact structure.

According to theinvention this result is attained by a pecular construction and arrangement of a diametrieally magnetized permanent magnet, the poles of'which are provided with pole pieces surrounding each other eoncentrically. The permanent magnet may, for instance, consist of an integral ring. On account of this arrangement the diameter and consequently the mass of the armature disc of the diaphragm may be chosen so small as it appears recommendable from an acoustic point of view (with respect to higher harmonics, 'damping of radiations, ete.) The diaphragm, which preferably consists of a thin foil of a non-magnetic material carries in a manner known per se an armature of a magnetic material in its central part. On account of the small f mass of the diaphragm it becomes possible besides damping the radiation also to damp the diaphragm effectively by means of an air-friction damping device. This device is preferably made adjustable in a manner which will be described more detailed hereinafter.

In the accompanying drawing two construetional forms of the invention are shown by way of examples.

Fig. 1 shows a longitudinal sectional view of a telephone which also may be employed as a loud speaker.

Figs. 2 and 3 show details of the device shown in Fig. 1.

Fig. 4 is a longitudinal sectional view through a form of the invention which is especially suited for persons hard of hearing.

According to Fig. 1 an annular permanent magnet 12 is arranged in a casing 1. The said magnet is magnetized diametrically. One side of the magnet, for instance, the north pole is connected to a perpendicularly arranged soft iron core 13 by means of a bracket 14 also of soft iron. Fig. 2 is a bottom view which shows the said bracket as well as the annular magnet 12. On the core 13 a winding 11 is arranged, the ends 22 of which, for instance, maybe passed out through the bottom of the casing 1. 'Between 52,934, and in Germany February 28, 1925.

the two halves of the annular magnet 12 and the bottom of the casing 1 a distance piece 21 is located, which is of the same height as the pole bracket 14. This spacing piece 21 could also be used for fastening the leading in cords 22. On the annular magnet 12 two spacving blocks 15, 16 are arranged one of which is made of brass, whereas the other (16), which is situated diametrically opposite to the pole bracket14, is made of soft iron. On the spacing blocks the pole disc 19 is arranged and the rim of the same is fastened to the blocks 15, 16, for instance, by means of screws. The central part of the pole disc rises perpendicularly from the dise rim and is equipped with a central bore through which the free end of the soft iron core 13 projects. The pole disc 19 is provided with a slot 20 (Fig. 3) in order to prevent eddy currents and to create a damping of the diaphragm. Above the free end of the core 13 an iron armature 6 is arranged, which is soldered Ato a diaphragm 4. This diaphragm has the form of a thin foil, and may, for instance, be made of phosphor-bronze. The diaphragm 4 is soldered to a supporting ring 5 from which it will hang down in a slack state when the ring is not mounted in position as shown. The supporting ring 5 also carries an annular member 17, which is formed with a downward directed collar 17 which stretches the diaphragm when being pressed against the same. Y

The rings 5 and 17 are pressed against each other by means of a flanged sleeve or ring 18. This ring is preferably of L-shaped crosssection and the upper flange is formed, after the rings 5 and 17 have been placed in the sleeve 18, by bending the upper rim inwardly over ring 17. By means of this body 18 the rings 5 and 17 are p'resed firmly together at their points of contact, whereby the collar 17 is pressed against the diaphragm. The extent of stretching of the diaphragm depends upon the height of the collar 17'. The device consisting of. the rings 5 and 17, the diaphragm 4 with the armature 6 and the body 18 is placed upon the peripheral part of the pole disc 19. The casing 1 is closed at its top, for instance, by a cover 3, which, for instance, may be screwed to the casing 1 and which is provided with a central bore 2. Y

In the embodiment of the invention shown in Fig. 4 the magnet system and the diaphragm are On theupper edge of the pot-shaped casing 1 the pole disc 19 is placed, which carries the entire magnet system. The magnet system 12, 13, 14, 16 is thus suspended in the casing 1. The outer rim of this pot-shaped casing has a screw thread, by means of which the threaded cap 23 may be fastened to it. The upper part of the cap is inwardly bent, so that it will press the diaphragm carrying parts against the pole disc 19. A disc 3 closes the casing 1 and is pressed downward by tlie cap 23. The disc 3 is preferably loosely arranged on the upper end of the body 18 and its central bore 2 is lying at an angle of 30 degrees to the plane ofthe disc. A projection 24 surrounds the said bore or opening and serves for connecting theY telephone to a suitable supporting device, which maybe inserted into the meatus of the ear. It is of course also possible to give the projection 24 such a form, that it may serve itself as a supporting device. j

The concentrical arrangement of the poleshoes as above described also gives a good support for the diaphragm and makes it possible to reduce the swinging mass considerably, because the armature 6 on the diaphragm only has to be of a diameter slightly greater than the diameter of the central bore in the pole disc 19. The ring shaped permanent magnet is especially advantageous, because a relatively long magnetic path is obtained even at small dimensions of the telephone. On account of this it is possible to choose such proportions between the length and the cross sectional area of the magnetic path that a suitable value of the apparent remanence will be obtained even when using the easily machinable tungsten steel for the magnet. It will therefore not be necessary to employ the hitherto used cobalt-chromesteel, which is very difficult to machine.

The slots or openings 20 (Fig. 3) Ain the' pole disc may be of any desired form. As alrcadymentioned these openings serve principally for giving the diaphragm 2 suitable damping. When oscillating the diaphragm must oscillate an amount of air through the slot in the pole disc, whereby mechanical frictional losses are produced. By giving the slot a suitable form it is in a simple way pos'- sible to obtain a diaphragm damping of a desired value. The effective cross section of the air gap which is formed through this slot .in the pole disc is preferably made adjustable. The adjustability may, for instance, be obtained by turning the diaphragm casing 18 to cover a greateror smaller portion of slot 20. If the air gap is made very narrowthe enclosed air volume will act as an air cushion. In this way the elasticity of the diaphragm is added to the elasticity'of this air cushion, wherebyas the mass reformed substantially as in Fig. 1.`

mains constantthe natural tone or frequency 'of the diaphragm is increased although the diaphragm performs frictional work by Way of the dislocation of the air. If now the opening is widenedv continually the elasticity of the air cushion decreases continually. The ineffective work will become prominent and the natural tone will sink correspondingly until at a certain critical size of the opening it will be of the same value aswith a diaphragm without an air cushion. If now the opening is further widened the tone will still deepen. In this case the ineifective work dominates. Finally the tonev remains at a certain pitch, until it again passes upward, because the ineffective work is reduced when the opening becomes very wide. At a very great opening the conditions will be the same as with an undamped diaphragm.

The forming of the diaphragm as a separate element of construction and the easy eX- changeability attained thereby makes the telephone especially suitable for persons hard of hearing. Such persons are generally eX- tremely hard of hearing within a limited range of frequencies. By adjusting a certain natural tone of the diaphragm of this new telephone it becomes possible to amplify highly just the frequency range which is especially difficult to. hear by the person in question, whereas the amplification of the remaining range is less intensive. Hereby it is of importance that the steepness of the resonance curve and the position of the maximum resonance may be adapted in each individual case by means of the adjustable damping. It is recommendableto plot an audi ility curve for this operation.

The new telephone may also be employed as a loud speaker, for instance, in the form shown in Fig. 1. In this case the natural tone should be higher than 1000.

What we claim as our invention and desire to secure by Letters Patent is 1. Telephone apparatus com rising a casing, a diaphragm consisting o -a thin metal foil, an iron armature provided on said foil, a support for said foil, means adapted to regulate the tension of said diaphragm, and an annular magnet system diametrically magnetized, provided with a slot in cooperation with said diaphragm.

2. Telephone apparatus comprising a casing, a cover screwed to the easing, a diaphragm consisting of a thin metal foil, an iron armature provided on said foil, a support for said foil, means adapted to regulate the tension of said foil, an annular diametrically magnetized permanent magnet, the poles of which having fixed thereon pole pieces, one piece concentrically surrounding the other.

3. In a telephone receiver the combination of a casing, a ringshaped permanent magnet positioned therein, an outer annular disc shaped pole piece, which closes the casing,

an inner pole piece disposed concentrically to and being surrounded at a small distance by the outer pole piece, anda thin metallic foil diaphragm, having a disclike iron armature fixed thereon, said diaphragm forming an i'r damping chamber With said outer pole isc.

4. In a telephone receiver the combination of a casing, an outer disc shaped annular pole piece, which closes the casing, an inner pole piece concentrically surrounded by the outer pole, a thin metallic foil diaphragm having a disclike iron 'armature fixed to and forming an air damping chamber with said outer pole piece, the latter having a slot, and means for varying the effective cross-section-of said slot.

5. In a telephone receiver the combination of a casing, an outer annular disc shaped pole piece, which closes the casing, an inner pole piece concentrieally surrounded by the outer pole, a thin metallic foil diaphragm with a disclike iron armature fixed thereon, the outer annular pole piece having an adjustable slot and a diametrically magnetized permanent annular magnet having its poles fixed to said pole pieces.

6. In a telephone receiver the combination of a casing, a diametrically magnetized annular magnet, an annular disc shaped pole piece connected to one magnet pole and closing said casing, and an inner pole piece connected to the other magnet pole and being located in the inner portion of and forming a small air gap with said annular pole piece, a

' metallic foil diaphragmhaving an iron disc armature fixed to it which bridges said air gap, said disc pole piece having a radial slot and means for adjusting the effective Width thereof, the central portion 'of said disc pole piece being raised above the plane of its peripheral portion.

7. In a telephone receiver the combination of a casing, a diametrically magnetized annular magnet, an annular disc shaped pole piece connected to one magnet pole and closing said casing, and an inner pole piece connected to the other magnet pole and being located in the inner portion of and forming a small air gap with said annular pole piece, a diaphragm carrier and a metallic foil diaphragm mounted therein, said diaphragm having an iron disc armature fixed to its central portion which bridges said air gap, said disc pole piece having its central portion raised above the plane of its peripheral portion and having a radial slot, said diaphragm carrier having a similar radial slot and being rotatable relatively to said disc, to adjust the effective Width of said disc slot.

8. In a telephone apparatus in combination with a tensioned diaphragm consisting of a thin metal foil, an iron armature centrally fixed thereon, of a diametrically magnetized magnet systemcomlprising an lntegral ring, a core fixed centrica ly to said ring and forming a small annular air ing one of its pole pieces, a circular pole piece mounted upon the ring forming the other pole piece, said circular pole piece having a circular cent-ral elevation, a central bore in said elevation arranged to receive said core to form an air gap therewith, bridged by said armature, and a slot in said pole piece.

9. In a telephone apparatus in combination with a tensioned thin metal foil having centrally fixed thereon an iron armature of a small size, of a diametrically lmagnetized magnet system comprising an integral ring, a core fixed centrally to said ring and fori ing one of its pole pieces, a soft iron spacer mounted on the other pole and carrying at its end a disc shaped pole piece, a central bore in said disc pole piece, said central bore being arranged to receive said core and form- 0 gap therewith, said disc pole piece having a slot radially extending from said bore.l

10. A telephone apparatus having in combination a tensioned thin metal foil diaphragm and an iron armature of a small size fixed thereon, an annular diametrically magnetized permanent magnet, a bracket lixed to one of lits poles and carrying a core stud centrally disposedrelatively to the annular magnet, a coil arrangedon said stud, a soft iron spacer attached to the other pole of the ring magnet and extending in parallel t'o but outside of said coil, a disc pole piece fixed to `said spacer, said disc consisting of a central raised portion and a peripheral flange, and serving as an abutment for the free end of said coil, va central bore in said pole piece arranged to receive said core stud and forming a small annular air gap therewith which is bridgedD by said armature, said disc having a slot radially extending from said bore and means adapted to regulate the eective Width of said slot.

11. In a telephone apparatus a casing having a cover screwed thereto, a diametrically magnetized permanent ring magnet, a bracket fixed to one of the magnet poles and serving as a ring base, and a core stud on said bracket disposed in the central axis of the ring magnet and forming one of its pole pieces, a coil resting on said bracket and being disposed on said core stud, a spacer of magnetic material attached to the other pole and extending in parallel to but outside of the coil, a second spacer of non-magnetic material similarly extending from the ring but on the other side of the coi a disc pole piece rigidly connected to both of said spacers, said disc having a Hange and a raised central portion and serving as an abutment for the free end of said coil, said central disc portion being provided With a bore Within said core stud is located, forming with said bore a small annular air gap, said disc also having a radial slot extending from said bore, a tensioned metal foil diaphragm spaced in which the end ofA iront of said disc and having fixed to its center an iron armature to bridge said annular air gap, a carrier for tensioning and holding said diaphragm in tensioned and spaced position, said carrier being supported by the flange of said disc pole piece, and means overlapping said carrier and being attached to said casing for pressing said carrier against the disc flange to hold the magnet system against the casing.

l2. In a telephone apparatus a pot-shaped casing having a flange and an inwardly flanged collar threaded thereon, a diametrically magnetized permanent ring magnet disposed in said casing, a bracket fixed to one of the magnet poles and a core stud on said bracket disposed in the central axis of the ring magnet and forming one of its pole pieces, a coil resting on said bracket and being disposed on said core stud, a spacer of magnetic material attached to the other pole and extending in parallel but outside of the coil, a second spacer of non-magnetic material similarly' extending from the ring but on the other side of the coil, a disc pole piece -rigidly connectedl to both of said spacers,

said disc having a flange and a raised central portion,l the outer flange portion resting on said casing flange and thereby rsupporting the magnet and coil structure, the inner flange portion serving as an abutment for the free end of said coil, the raised dise portion having a central bore containing the core stud end and forming a small annular air gap with the latter, said disc also having a radial slot extending from its central bore to its periphery, a diaphragm casing resting upon said dise flange and containing a metal foil diaphragm, a collar holding said diaphragm at its periphery and a tensioning ring for the diaphragm of smaller diameter than the collar, said tensioning ring being held by the diaphragm casing against the diaphragm, thereby tensioning it, said diaphragm havingr an iron armature fixed to its center and being suitably spaced from said core and bridging said annular gap, said diaphragm casing having a radial slot registerable with said disc slot to vary the effective Width of the latter, a cover plate with a central sound opening over said diaphragm casing, said cover plate, diaphragm casing and disc fiange being clamped against the casing flange by said threaded inwardly flanged casing collar.

13. A telephone apparatus comprising a diametrically magnetized magnet system having a. disc shaped pole piece, provided with a radially extending slot., and an adjustably mounted metal foil diaphragm carrying the iron armature of said magnet system, and being spaced from said pole piece and cooperating With said slot to produce the desired air damping of the diaphagm, and means for varying the effective cross-section of said slot by adjusting said diaphragm.

In testimony whereofwe atlix our signatures.

HELMUT SELL. BERNHARD LANGENBECK. 

